Does tapping a land for mana use the stack?

Mana abilities are a special category of activated (or triggered) abilities that produce mana as part of their effect. By rule, mana abilities do not go on the stack and cannot be responded to — they resolve immediately when activated. This is defined in CR 605.3a.

A land's tap-for-mana ability qualifies as a mana ability because it is an activated ability that could produce mana and does not have a target (CR 605.1a). Because it meets these criteria, it bypasses the normal stack process entirely.

This is an intentional design exception to the general rule that activated abilities use the stack (CR 602.2). It allows players to produce mana quickly without opponents getting a window to respond before the mana enters your mana pool.

Concrete example: You tap a Forest to add one green mana. Your opponent cannot cast Stifle or any instant in response to this activation — by the time either player could take another action, the mana is already in your mana pool.

Note that this only applies to mana abilities. If a land has an activated ability that does not produce mana (such as a Mishra's Factory animating itself), that ability does use the stack normally and can be responded to (CR 602.2).